It has been proposed to use changes in the light emitted by a body of temperature-dependent photo-luminescent material as a measure of the temperature at a remote location, by making the body luminescence through the supply of excitation light to it and to determine the temperature of the body by sensing a parameter of the luminescent light received from the body. It has been proposed to use a common light guide fiber for transmitting the excitation and luminescent light, to and from the body.
This invention relates to an extension of this prior proposal by using a body that permits a parameter of the luminescent light to be affected electrically, and thereby enables signal information relating to a range of different values sensed at one location to be transmitted to a remote location.
The references to "light" in this specification should be taken to include electromagnetic radiation which is not necessarily in the visible region of the spectrum, and references to "photo-luminescence", "photo-diode" and "light-emitting diode" (or "LED") should also be taken to include properties and devices operating in regions outside the visible spectrum (e.g. in the IR and UV).